Protecting unit for oil filled submergible motors



OGL 2, 1951 A. ARuTuNor-F 2,569,741

PROTECTING UNIT FOR OIL FILLED SUBMERGIBLE MOTORS Filed Feb. 9, 195o 2 Sheet's-Sheet 1 fx--W r1 dpa/wc INVENTOR. A.Aru Zan Qjj" 2 Sheets-Sheet 2 ATTORNEYS Oct. 2, 1951 A. ARUTUNOFF PROTECTING UNIT FOR OIL FILLED SUBMERGIBLE MOTORS Filed Feb. s, 195o M m/ 7m 4. 4 m w 0J Z an W, E A. M o ff w y. m

Patented Oct. 2, 1951 PROTECTIN G UNIT FOR OIL FILLED SUBMERGIBLE MOTORS Armais Arutunoff, Bartlesville, Okla., assignor to Reda Pump Company, Bartlesville, Okla., a corporation of Delaware Application February 9, 1950, Serial No. 143,269

19 Claims.

`This invention consists in improvements in a protecting unit for oil iilled submergible electric motors and is primarily directed to an assembly for use in connection with electric motors employed in oil well operations such as the pumping of deep wells, where the motor is disposed in the Well,'at the lower end of a casing which houses the coaxial pumping and motor protecting units.

With submergible motors in this type of operation, there is usually employed an oil filled lubrieating and protecting unit or reservoir which is interposed between the pumping unit and the motor, such, for example, as those illustrated in my former U. S. Patents Nos. 1,855,264 and 1,970,484. As explained in those patents, due to the normal expansion and contraction of the oil in thefrnotor and motor protecting unit, resulting from the starting and stopping of the motor, ther-e is a tendency for the surrounding well iluid to leak into the protecting and lubricating resservoir and ultimately to find its way along the motor shaft to the motor unit. Hence, it is necessary tothe successful operation of the system, to provide some means for insuring against the entrance of damaging moisture into the motor structure, two such means being illustrated and described in my said former United States patents.

It is the primary obj-ect of my present invention to provide a motor protecting unit which is a marked improvement over structures previously known to me, including my former units, and which will afford a maximum of protection against moisture from the surrounding well fluid,

gaining access to the motor by traveling along the motor shaft.

To this end, I have devised a novel arrangement of one or more collapsible elements disposed n the lubricating reservoir and defining therein, separate pressure zones, respectively subjected to the pressure existing in the reservoir and that of the well fluid surrounding the reservoir. The collapsible element or elements are sealed between the respective zones and are responsive to variations in the pressure diierential of the lubricating medium in the reservoir and the well fluid surrounding the reservoir so as to compensate for contraction and expansion of the lubricant resulting from such variations andthus prevent access of the surrounding well :fluid to the motor shaft.

In one form of the invention, the protecting element comprises a single collapsible cylinder of suitable material to withstand chemical attackeither by the lubricant or the well uld, and

arranged concentrically in the reservoir surroundingI the motor shaft. The extremities of this cylinder are sealed to provide two separate zones, one in communication with the interior of the reservoir and the other, with the area surrounding the reservoir. f

Another form of the invention embodies one or moreV collapsible breathing bags or receptacles which are disposed within the protecting and lubricating'iuid in the protecting unit, with their interiors in communication with the surrounding well fluid, and their external surfaces responsive to the expansion and contraction of the iluid in the protecting unit. Thus, any well uid with its contained moisture, which would normally be drawn into the protecting unit by Variations in dirferential pressure when the motor is stopped', will be retained in the collapsible receptacle and expelled therefrom into the well, when the motor is again started. f

In connection with both forms of the invention, I provide resilient means to maintain a normally xed reserve capacity in the zone or zones containing the lubricating medium so as to allow for breathing when the motor is initially started and stopped and t-o prevent complete collapse of the zone-defining element. These means may comprise a series of taut springs longitudinally supported at spaced intervals around the inner wall of the collapsible cylinder in the rst form of the invention, while in the second form, portions of the walls of the individual collapsible receptacles may be thickened or provided with spring inserts, to accomplish this function.

The foregoing as well as other objects, will be made more apparent as this description proceeds, especially when considered in connection with the 'accompanying drawings which illustrate two forms of my invention and wherein numerals of like character designate similar parts throughout the several views.

In the drawings:

, Figure l is a vertical sectional View through a motor protecting and lubricating unit embodying one form of my invention wherein a single collapsible cylinder is employed for defining the separate zones;

Figure 2 is a transverse sectional view taken on line 2,-2 of Figure 1 Figure 3 is a vertical sectional view through a motor protecting and lubricating unit constructed in accordance with the second form of my invention, the collapsible receptacles therein being shown in expanded condition;

I) 'gure e is a similarI View showing the collapsible ioceptacles in contracted condition;

Figure 5 is a transverse sectional view taken on line 5-5 of Figure 3; and

Figure G is a detailed View of one of the collapsible receptacles, shown partly in section to illustrate the interior thereof.

Referring to Figure l of the drawings, designates a cylindrical housing for the lubricating and protecting unit, said housing being closed at its upper end by a head S, reduced and threaded at its lower extremity 9 to engage complementary threads in the housing I. The lower end of the housing l is closed by a base I5, similarly reduced and threaded at its upper Gnd i I, to engage complementary threads in the housing l'. The central portions of the head 8 and base IS are provided with co-axial openings 52 and I3 respectively, to accommodate the shaft section I4 which connefi's the shaft of the pump unit with the motor shaft. Fragmentary sections of a pump uni id motor unit are shown connected to the top and bottom respectively of the protecting unit.

A bushing I5 is fitted into the opening I2 in the head 8 and rotatably supports the upper end of the shaft section I4, the lower end of said bushing being provided with an annular recess I6 which receives the reduced upper end of a shedder II, mounted on and rotatable with the shaft I4. The lower end of the shedder II is in the form of an apron which envelopes and overhangs the top of a stand tube I8 which surrounds the intermediate portion of the shaft section I4 in spaced relation, and is supported at its lower 1F end in the opening I3 in the base I0. Thus, the stand tube I8 forms within the housing 1, an annular chamber, separated from and surrounding the shaft I4.

The upper end of the shaft section I4 is splined as at I9 or otherwise suitably formed for operative connection to the lower end of the pump unit shaft (not shown in the drawing), and the lower end of the shaft section I4 is similarly splined as at 20 for connection to the vertical motor shaft. The lower end of the shaft section is preferably rotatably supported in a bearing member 2|, mounted in the base I0, said bearing being provided with at least one vertical passageway 2Ia whereby the area surrounding the shaft section I4 is in communication with the interior of the motor casing connected to the base I0.

At the upper end of the shaft section I4, I may provide a spring loaded seal 40 adjacent the bushing I5, for the purpose of minimizing the intermingling of the liquids in the motor and reservoir, with those in the pump unit above the shaft section I4. However, as will later appear, if a sufliciently high pressure is developed in the reservoir to overcome the spring load of seal 40, a certain amount of escape along the shaft I4 will be permitted.

Coaxial with the stand tube I8 and spaced outwardly therefrom is an annular partition 22 supported at opposite ends in annular retaining discs or rings 23 and 24, sealed transversely within the housing 1, at predetermined `points spaced longitudinally respectively, from the head 8 and base I0. Also coaxial with the shaft I4 and stand tube I8, is a collapsible cylinder 25, the extremities of which embrace oppositely disposed, longitudinally extending anges 23 and 24', inwardly spaced on the retaining rings 23 and 24 respectively, where the ends of the cylinder are secured '.f. di)

by any suitable means such as wrapping with linen thread or the like to afford a sealed connection.

Inasmuch as the cylinder 25 is subjected to contact with the lubricating fluid within the protecting reservoir as well as the surrounding well fluid, as will hereinafter appear, it must be composed of a flexible material which is not vulnerable to chemical attack by either of these fluids. Various materials are adaptable for this purpose and in the preferred form of my invention, I ernploy a material such as neoprene which has the desirable properties of flexibility and will withstand chemical attack.

The annular partition 22 is provided with one or more apertures 26 placing the area within the cylinder 25 in communication with the reservoir R which contains the lubricating medium, and if desired the rings 23 and 24 may be apertured as shown in Figure '1. Likewise, the housing 'I is provided with one or more openings 21 placing the area surrounding the cylinder 25 and within the housing, in communication with the surrounding well fluid in which the housing is disposed. Thus the collapsible cylinder 25 is responsive to the pressure differential of these areas.

In order to prevent the complete collapse of the cylinder 25 and to maintain over a period of years of operation, a normally fixed reserve capacity within the cylinder, so as to allow for breathing when the motor is started and stopped. I preferably provide a series of resilient members such as coil springs 28, normally stretched taut between radially disposed arms 29, fastened as by welding to the outer wall of the annular partition 22. Opposite ends of these springs are secured in eyes on the ends of respective arms 29, so that normally the springs 28 lie parallel with the inner face of the collapsible cylinder 25 as shown in the full lines in Figure 1. It will be apparent that the springs 28 offer a resistance to inward pressure on the cylinder 25 which neutralizes the pressure differential on the two sides of the cylinder, yet the springs are suiciently side of the cylinder versus lubricant on the inside of the cylinder.

As the original expansion of the lubricant may create excessive pressure inside the motor structure and in the reservoir R, I may provide a relief valve 30, adjacent the lower portion of the reservoir. In actual practice, I have found this arrangement more practical than relying on the spring loaded seal 40 previously referred to.

The upper end of the housing is provided with a vent plug 3| preferably located in the head 8, to permit escape of air during the filling operation which is accomplished through a combined fill and drain plug 4I situated in the base I0.

The operation of this form of my invention will be apparent. The motor and the reservoir R are first filled with a suitable lubricant through the valve 4I, the vent plug 3I being opened for this purpose. The lubricant entering through plug 4 I, fills the motor unit and rises through the passageway 2Ia in bearing 2U, until the reservoir R, comprising the area surrounding the shaft I4. is lled, any surplus lubricant being automatically discharged through relief valve 30. When the motor starts the oil in the reservoir R gradually expands andthe cylinder 2511s extended to limits of the inner wall of the housing 1. Upon stoppage of the, motor, the fluid in the. reservoir R naturally contracts and reduces in volume, and the water or` other. surrounding well fluid, which would otherwise be drawn into the reservoir and mixed with the oil or protecting fluid, enters the space within the .housing 1 surrounding the cylinder 25fand forces the cylinder inwardly to compensate for. the loss of volume in the reservoir. However, this `water or surrounding well fluid is retained inthe lspace around the cylinder 25 and is preventedfromfcommunicating with the oil in the reservoir, so as to contaminate the shaft and ultimately the .motor structure, by gaining access to those points alongthe shaft.Y Y A f. f

Asbefore pointed out, the taut springs 28 prevent complete collapse of the cylinder 25 and permit breathing not only during the initial starting and stopping operation but for a prolonged period. When the motor is again started theA oil in reservoir R naturally expands and with it, the flexible cylinder 25, which forces a volume ofthe surrounding fluid back into the Well, equal to. that previously drawn into the housing. It maybe stated that if, during the operation of the motor and pump, a slight over-balance of the pressure inside the cylinder 25 occurs, and some oozing .ofr oil takes place along the shaft, the elasticity of the springs 28 tends to establish an equilibrium or balance of pressures vinside and outside the cylinder. Thereafter, the structure is in permanent operating condition.

Referring to Figures 3 to 6 which illustrate a second embodiment of myinvention, it will be seen that within the reservoir R formed by the housing 1, I provide one or more breathing bags or,V collapsible receptacles 32, the form of my invention illustrated, embodying twosuch receptacles.` Inasmuch as the receptacles 32 are disposed `within the protecting and lubricating fluid with which the reservoir R is filled, they must, as in the case of cylinder 25 be composed of a flexible material which is not vulnerable to chemical attack either by the oil or the well fluid. Various materials are adaptable for this purpose and in the preferred form of my invention I employ a material such as neoprene which has the desirable properties of ilexibility and will withstand chemical attack. These bags 32 may be cylindrical in cross section or oval as shown in Figure 5, their upper ends terminating in an open neck adapted to be secured to the lower end 33 of an adapter 34 which is threaded to engage acomplementary threaded opening 35 in the head 8, a passageway 36 through the head 8, placing the opening 35 and the adapter 34 in communication with the area surrounding the protecting unit housing 1. The neck of the bag 32 may be secured to the adapter 34 in any suitable manner, in the present instance, a series of wrappings of waxed linen stringvbeing employed, as clearly shown in the drawings.

In order to fill the reservoir R with a lubricatingy and protecting fluid, a drain 4and fill valve 4I of any suitable design, is provided at the lower end of the reservoir, in the base I as shown in Figure 3 and, although it is not shown in this figure, a vent plug may be provided at the upper end of the reservoir preferably extending through the head 8, as shown in Figure 1, to permit the escape of air during the filling operation.

When the reservoir R is filled with lubricating and protecting fluid through the vdrain and fill valve 4|, vthe bag or bags 32 naturally collapse and, in order to preventv a complete collapse. of these bags so that their inner surfaces have a tendency to adhere to one another, Iprovide an endless coil spring 31 which is vertically disposed in each bag and rests upon the bottom of the bag, extending substantially .to the upper. extremityof the bag. Thus, when the bags are collapsed as shown in Figure 4, there is maintained throughout the longitudinalextent of each bag, an open area for the admission of the surrounding well fluid, as will be later explained.

Furthermore, as inthe first form of my invention, it is desirable toy constantly prevent the bag or bags v32 .from becoming completelyy collapsed, and particularlywhenthe reservoir R is rst filled, so asto allow for breathing due to variations. in static pressure inside and outside the reservoir. To this end, theupper portion of each bag is provided with a thickened or stiftened area 3B the lower end of which gradually tapers to the normal thickness of the bag wall. This ,thickened or stiffened area has sufficiently resistant properties to prevent complete collapse of the bag and to provide av normally xed reserve capacity in the upper portions of each bag so as to allow for breathing necessitated by minor variations in static pressurewithin the reservoir R and ink the area surrounding the protection unit. While I have shown and describedy these bags as being provided with thickenedportions for the purpose set forth, it will be understood that I do not intend to confine myself to this particular embodiment. Obviously, other means such as resilient springs maybe interposed in or operatively associated with the upper portions of the bags to maintain this fixed reserve breathing capacity.

While I have shown a reservoir embodying two collapsible receptacles it will be obvious that I may employ more or less, according to the requirements of successful operation of the unit in compensating for variations in the probable pressure differential involved. Likewise, the shape of the receptacles may be varied to meet different conditions of structure and operation.

The operation of this form of my invention will `be obvious from the above description of the structure involved. However, this operation may be briefly described as follows:

At the time the pump unit, protecting unit and motor unit are assembled for lowering into the Well, the motor casing and reservoir R are filled with suitable lubricating and protecting fluid through the drain and fill valve 4I, the vent plug (not shown) being open for this purpose. The filling of the reservoir collapses the bag or bags 32 with the exception of the xed reserve space in the upper portions of the bags, the endless coil spring preventing complete collapse to maintain a continuous air space on either side, from top to bottom of the bag. This prevents the bag walls from adhering together and interfering with the proper breathing operation.

When the motor starts the oil or other protecting fluid in the reservoir R gradually expands and oozes along the shaft I4, thus losing some of its volume. The interior of each bag is in communication with the fluid surrounding the housing 1, through the adapter 34 and passageway 36. Thus, when the motor is stopped, and the iluid in the reservoir R naturally contracts and reduces in volume, the water or other surrounding well fluid, which would otherwise be drawn into the reservoir and mixed with the oil or protecting fluid, enters the bag or bags through passageway 36 and adapter 33, replacing the lost volume in the reservoir R. This water or surrounding well iiuid is retained in the bags and prevented from comingling with the oil in the reservoir, so as to contaminate the shaft and ultimately the motor structure by gaining access to those points along the shaft.

When the motor is again started the oil in the reservoir R naturally expands and expels the well uid which has been previously drawn into the bags, to the extent of the remaining volume of oil in the reservoir. Thus, if any oil has been lost during the preceding operating period of the pump, an equivalent volume of water will remain in the bag. However, this will not jeopardize .the lubricating and protecting functions of the remaining oil for, due to the displacement of partially filled bags, the area of said reservoir will be completely lled on the exterior of said bags.

In both forms of the invention, as an added precaution against foreign substances descending along 'the shaft I4 from the upper end of the stand tube I8, the skirt of the shedder il overhangs the top of the stand tube as shown in Figures l, 3 and 4, so that any material oating on top Aof the oil in the reservoir R is excluded from the stand tube and cannot gain access to the motor.

VWith either form of my invention, surplus lubricant is discharged through a relief valve 3i] at the initial start and thereafter, differential pressures of negligible intensity compensate for all expansion and contraction of volume of the lubricant in the motor and reservoir. Although some over-pressure may exist at the commencement of operation, if some protecting fluid escapes along the shaft the flexibility of the collapsible element or elements, soon causes the pressure to become equal to the difference in specic gravity of the surrounding well fluid, against that of the lubricant in the reservoir, for a height of column equal to the height of the protecting unit. The pressure differential in my improved structure normally amounts to a few inches of water column when length of the protecting section, measured from the packing around the shaf to the bottom of the protecting chamber is two or three feet and when the unit is submerged in the surrounding well uid. As soon as the resilient stiffened areas 38 have neutralized that small pressure, equilibrium is established and the motor can operate uninterruptedly for an indefinite period.

Brieiiy stated, my design is fundamentally a low pressure protecting unit which, after some period of operation, becomes a permanent protecticn which is independent of the length of the motor below the protecting means.

From the foregoing, it is believed that my invention may be readily understood by those skilled in the art without further description, it being borne in mind that numerous changes may be made in the details of structure without departing from the spirit of the invention as set forth in the following claims.

I claim:

l. In a protecting unit for an oil filled, electric mot-o1` assembly adapted to be submerged ina surrounding well fluid for driving a pump located above, and including a casing, a vertical motor and motor shaft extension concentrically disposed in said casing, and a closed reservoir in said casing surrounding said shaft extension above saidmotor, for containing a protecting and lubricating medium; means to compensate for expansion and contraction of said medium, incident to starting and stopping said motor, said means comprising at least one collapsible element disposed in said reservoir and defining therein, two laterally separated pressure zones, extending longitudinally substantially from end to end of said reservoir, the zone on one side of said aleinent beingv in communication with the medium in the reservoir and the zone on the other side of said element being in communication with the fluid surrounding said casing, whereby said element is yresponsive to variations in the pressure diiierential oi' said iiuid, so as to permit the entrance into one of said pressure zones, of a volume of fluid equal to the volume of medium lost from said other zone by contraction of said medium and to thereafter expel a proportionate volume of said fluid on expansion of said medium.

In a protecting unit for an oil iilled,'electric motor assembly adapted to be submerged in a surrounding well iuid and including a casing, a vertical motor and motor shaft concentrically disposed in said casing, and a closed reservoir in said casing surrounding said shaft above said motor, for containing a protecting and lubricating medium; means to compensate for expansion and contraction of said medium, incident to starting and stopping said motor, said means comprising a collapsible cylinder disposed in said casing,'con centric with said shaft with its longitudinal extremities sealed to form in said casing, the peripheral boundary of said reservoir, the outer surface of said cylinder being exposed to the pressure of the well fluid surrounding said casing, through an aperture in the latter, whereby said cylinder is responsive to variations in the pressure differential of the medium in said reservoir and said surrounding fluid, so that the area in said casing encircling said cylinder, receives a volume of iiuid equal to the volume of medium lost in said reservoir by the contraction of said medium and to thereafter expel a proportionate volume of said fluid on the expansion of said medium.

3. Apparatus as claimed in claim 2 wherein said collapsible cylinder is secured in place by a pair of longitudinally spaced annular retainers fixed adjacent the extremities of said casing in concentric spaced relation to said shaft.

4. In a protecting unit for an oil filled, electric motor assembly adapted to be submerged in a. surrounding well fluid and including a casing, a vertical motor and motor shaft concentrically disposed in said casing, and a closed reservoir in said casing surrounding said shaft above said motor, for containing a protecting and lubricating medium; means to compensate for expansion and contraction of said medium, incident to starting and stopping said motor, said means comprising a pair of longitudinally spaced annular retainers fixed adjacent the extremities of said casing in concentric spaced relation to saidy shaft, said retainers being provided with oppositely disposed annular flanges intermediate the radial extremities thereof, a collapsible cylinder disposed in said casing concentric with said shaft with its longitudinal extremities sealed around respective annular flanges of said retainers, to form in said casing the peripheral boundary of said reservoir, the outer surface of said cylinder being exposed to the pressure of the well fluid surrounding said casing, through an aperture in thelatter, whereby said cylinder is responsive to variations in the pressure differential of the medium in said reservoir and said surrounding fiuid, so that the area in said casing encircling said cylinder, receives a volume of fluid equal to the volume of medium lost in said reservoir by the contraction of said medium and to thereafter expel a proportionate volume of said fiuid on the expansion of said medium.

5. In a protecting unit for an oil filled, electric motor assembly adapted to be submerged in a surrounding well fluid and including a casing, a vertical motor and motor shaft concentrically disposed in said casing, and a closed reservoir in said casing surrounding said shaft above said motor, for containing a protecting and lubricating medium; means to compensate for expansion and contraction of said medium, incident to starting and stopping said motor, said means comprising a pair of longitudinally spaced annular retainers fixed adjacent the extremities of said casing in concentric. spaced relation to said shaft, said retainers being provided with oppositely disposed annular fianges intermediate their extremities, a cylindrical partition supported between said retainers in spaced relation t said shaft, a collapsible cylinder disposed in said casing concentric with said shaft and partition, with its longitudinal extremities sealed around the respective annular fianges of said retainers, to form in said casing, the peripheral boundary of said reservoir, the outer surface of said cylinder being exposed t0 the pressure of the well fiuid surrounding said casing, through an aperture in the latter, whereby said cylinder is responsive to variations in the pressure differential of the medium in said reservoir and said surrounding fluid, so that the area in said casing encircling said cylinder, receives a volume of fluid equal to the volume of medium lost in said reservoir by the contraction of said medium and to thereafter expel a proportionate volume of said iiuid on the expansion of said medium.

6. Apparatus as claimed in claim including resilient means cooperating with said collapsible cylinder to prevent complete collapse thereof.

7. Apparatus as claimed in claim 5 including a. series of spring elements extending longitudinally parallel to the walls of said cylinder, said springs being secured at their opposite ends between respective pairs of radially disposed sup- V porting arms fixed at intervals around the periphery of said cylindrical partition, to prevent complete collapse of said collapsible cylinder.

8. A self-contained protecting unit for submergible, oil filled, vertical electric motors, comprising a closed cylindrical casing adapted to be coaxially interposed between a pumping unit and a motor unit, a shaft section concentrically disposed in said casing, for connection to the respective adjacent ends of the shafts of the motor and pump units, said casing forming a reservoir for a protecting and lubricating medium, at least one collapsible receptacle depending in said reservoir alongside said shaft section and disposed in the medium within said reservoir, with its interior sealed with respect to the reservoir but in communication with the fluid surrounding the reservoir, said receptacle being responsive to variations in the pressure differential within and without said reservoir, whereby any of said surrounding fiuid which enters said reservoir in replacement of lost volume due to contraction of said medium, will be confined within said collapsible receptacle until ejected therefrom by expansion of said medium.

9. A protecting unit as claimed in claim 8, including resilient means associated with the walls of said collapsible receptacle to resist complete collapse thereof under predetermined pressure variations and te thereby maintain a normally fixed reserve breathing capacity within the reservoir.

10. A protecting unit as claimed in claim 8, wherein a portion of walls of said collapsible receptacle is thickened to form an area having sufiiciently resistant properties to prevent complete collapse of the receptacle under predetermined pressure variations, t0 thereby maintain a normally fixed reserve breathing capacity in the receptacle.

11. A protecting unit as claimed in claim 8, wherein the upper area of the Walls of the collapsible receptacle is thickened to form an annular section having sumciently resistant properties to resist complete collapse of the receptacle under predetermined pressure variations, to thereby maintain a normally fixed reserve breathing capacity in the upper portion of the receptacle.

12. A protecting unit as claimed in claim 8, including means Within the collapsible receptacle for preventing complete collapse thereof.

13. A protecting unit as claimed in claim 8, including an endless coil spring disposed vertically within said collapsible receptacle to prevent complete collapse thereof.

14. A protecting unit for submergible, oil filled, vertical electric motors, comprising a cylindrical casing, a head closing the upper end of said casing, a base closing the lower end of said casing, means associated with said head and base respectively, for coaxially interposing said casing between a pump unit and a motor unit, said casing forming a reservoir surrounding a portion of the motor and pump shaft and adapted to receive a protecting and lubricating medium, a passagewayextending through said head from the area surrounding said casing to the interior ofthe reservoir, an adapter mounted in the inner extremity of said passageway, a collapsible receptacle carriedby said adapter and suspended from said head inte said reservoir, said receptacle communicating with the area surrounding said casing, through said passageway and adapter, with its interior sealed with respect to the interior of the reservoir, said receptacle being responsive to variations in the pressure differential within and without said reservoir, whereby any of said surrounding fiuid which enters the reservoir in replacement of lost volume due to contraction of said medium, will be confined within said collapsible receptacle until ejected therefrom by expansion of said medium.

15. A self-contained protecting unit for submergible, oil filled, vertical electric motors, comprising a cylindrical casing, a head closing the upper end of said casing, a base closing the lower end of said casing, a central shaft section rotatably mounted in coaxial openings in said head and base, means associated with said head and base, respectively, for coaxially interposing said casing between a pump unit and a motor unit, means at the extremities of said shaft section for interposing the same between the pump shaft and the motor shaft, said casing forming a reservoir surrounding said protecting unit shaft section, and adapted to receive a protecting and lubricating medium, and a collapsible receptacle disposed in said reservoir with its exterior exposed to the medium therein and its interior in lli.

communication with the fluid surrounding said casing, whereby said receptacle is responsive to variations in the pressure differential of said medium and said uid, so as to receive a volume of fluid equal to the volume of medium lost by contraction of the latter and to thereafter expel a proportionate volume of said fluid on expansion of said medium.

16. A self-contained protecting unit for submergible oil-filled, vertical electric motors, comn prising a cylindrical casing, a head closing the upper end of said casing, a base closing the lower end of said casing, a central shaft section, having its opposite ends projecting through and rotatably mounted in respective coaxial openings in said head and base, means respectively associated with said head and base, for coaxially interposing said casing between a pump unit anda motor unit, means at the projecting extremities of said shaft section Yfor concentrically connecting the latter -between the respective shafts of said pump and motor units, said casing forming a reservoir surrounding said central shaft section, andadapted t0 receive a protecting and lubricating medium,

means in said reservoir to compensate for exz.

pansion and contraction of said medium, incident to starting and stopping said motor, said means comprising at least one collapsible element disposed in said reservoir and defining therein, a

medium receiving zone in communication with` the interior of the reservoir, and a separate well fluid receiving zone in communication with the fluid surrounding the reservoir and sealed against the medium in the latter, said collapsible element being responsive to the pressure of the medium in said reservoir and that of the surrounding well uid, whereby any variations in the pressure dilferential of said medium and said surrounding uid is compensated for and access of said surrounding fluid to said shaft section is prevented.

17. In combination with a submergible 'oilfilled vertical electric motor unit and a coaxial pump unit, a self-contained protecting unit adapted to be coaxially interposed therebetween and comprising a cylindrical casing, a head closing the upper end of said casing, a Ybase closing Vthe lower end of said casing, a central shaftscctionhaving its opposite ends projecting through and rotatably mounted in respective coaxial openings in said head and 'base, means respectively associated with said head and base for connecting said casing to the pump and motor units, means at the projecting extremities of said shaft section for concentrically connecting the latter between the respective shafts of said pump and motor units, said casing forming a reservoir surrounding said central shaft section, and-adapted to receive a protecting and lubricating medium, means in said reservoir to compensate for expansion and contraction of said medium, incident to starting and stopping said motor. said means comprising at least one collapsibleelement disposed-in said reservoir and defining therein, ya medium receiving zone in communication with the interior of the reservoir, and a separate well uid receiving zone in communication with the 'fluid surrounding the reservoir and sealed against the medium in the latter, said collapsible element being responsive to the pressure of the medium in said reservoir and that of the surrounding well uid, whereby any variations in the pressure differential of said medium and said surrounding fluid is compensated for and access of said surrounding fluid to said shaft section is prevented.

18. The combination as claimed in claim 17 wherein said pump unit is mounted above and said motor unit is mounted below said protecting unit.

19. VA self-contained protecting unit as claimed in claim 16, including means to prevent the complete collapse of said collapsible element.

ARMAIS ARUTUNOFF.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS `Number Name Date 1,879,628 Mendenhall et al. 'Sept. 27, 1932 2,002,916 Mendenhall et al. 'May 28, 1935 

